It is the common practice, in an industrial steel-making plant, to have melting furnace structure with an off-gas duct system for conducting gaseous effluent away from the furnace. The gaseous products from the furnace are caused to move through the duct system by the draft created from the high temperature melting process within the furnace and also by suction means, usually in the form of an industrial fan, provided upstream on the effluent processing system. It is of critical importance to maintain a constant negative pressure within the furnace during the melting process and it is typical to monitor the furnace internal pressure through the use of one or more sensors installed in the furnace roof. Data input from such pressure sensors can then be used to regulate the pressure within the furnace by regulating the volume of effluent flow through the duct system.
The problems of utilizing sensors in the furnace structure have long been recognized. Frequent repair or replacement of sensors is required because they are subjected directly to the extreme high temperatures and destructive action occurring within the furnace. Such problems can only be solved by the provision of a new and improved method and apparatus for monitoring the gaseous pressure within a melting furnace and maintaining the pressure within a desired range without subjecting the sensing and control components to the intense internal furnace environment.